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Why temperatures at night are going up around the world and what we can do about it

Kate Doyle,
Thursday July 19, 2018 - 06:06 EST

Overnight lows are getting hotter in parts of the world, including Australia.
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History was made in the Middle East on June 28 when the world's hottest night on record was set in Quriyat, Oman with the overnight "low" dropping to 42.6 degrees Celsius.

Oman's hot night is just .

Individual location records have been broken in the US, Russia, Canada, Scotland, Armenia and Georgia.

Africa could have reached its highest ever reliably recorded temperature of 51.3C in Ourargla, Algeria on July 5.

The World Meteorological Organisation recognises 55C as the highest temperature for Africa, recorded at Kebili, Tunisia on July 7, 1931.

But there is widespread scepticism about the record's accuracy because the temperatures recorded before the 1950s are mysteriously higher than anything to have come after them.

Why warm nights are a problem

When it comes to heatwaves, the If it stays above the mid-20s, overnight sleep can become difficult because the .

University of New South Wales PhD student James Goldie, who is researching how temperature relates to health, said comfortable overnight temperatures were important in making sure people got a restful sleep.

"[It] is when our muscles recover from exercise. It's when our brains consolidate memories," he said.

"When night-time temperatures continue to be hot, when that heat just runs all the way through the night and onto the next day, we don't get that recovery, and that's when heat stress really starts to build up."

Mr Goldie said .

"They're like rips at the beach; if you respect them, they're tough but they're manageable. If you don't respect them, they can kill people," he said.

Over the past few weeks Canada has been experiencing summer heatwaves, with local news outlets now .

Nights are getting warmer

Research published in the International Journal of Climatology last year found night-time temperatures were increasing more rapidly than daytime temperatures.

According to the findings, minimum temperatures have been increasing at a rate of about 0.07 degrees per decade, compared with about 0.05 degrees per decade for maximum temperatures globally, for the period from 1960 to 2009.

Researchers proposed this was because night-time temperatures were more easily affected by an increase in greenhouse gasses.

Australia is not immune from warmer nights â€”and they are expected to continue to rise.

As part of the a threshold calculator has been created for the public to explore future climate scenarios.

The tool suggests an increase in over-25C degree nights into the next century, to different extents based on the different models and emissions scenarios.

Mr Goldie said some of the impacts of heatwaves from climate change could not be avoided.

"They're happening. But we can control how bad they get, and the actions we take to reduce CO2 now will save people's lives later down the road," he said.

high greenhouse emission scenarios are projected to increase heat-related deaths in Oman, where it was so hot a few weeks ago.

What can we do about it?

Aside from reducing greenhouse gas emissions, there are things we can do to mitigate the impact of heatwaves.

Monash University climate scientist Stephanie Jacobs said the best strategy to help reduce night-time temperatures was to plant trees and vegetation and keep them watered.

"When there are no trees, the sunlight heats up the ground," she said.

"When there are trees, the energy from the sun is diverted to helping the water in plants evapotranspirate instead of heating the surface, so it becomes cooler.

"As a result, the ground holds less energy during the day and then emits less heat at night."

Ms Jacobs said tree planting could be hard in desert environments, but it could be effective in cities.

"Plant more parks, gardens [and] lots of trees â€¦ it's been found that a mix of vegetation is the best because different plants have different benefits," she said.

Making buildings more reflective was another action Ms Jacobs suggested could assist in cooling temperatures.

"What I've looked at in my research is if all of the rooftops in Melbourne were white, and we basically turn Melbourne into a giant ," Ms Jacobs said.

"I would say if you're getting a new house, try and get the lightest colour roof possible."

Ms Jacobs said painting the roof white or with highly reflective paint was another option.

"This means that you reflect all the solar radiation away rather than having the rooftop absorb it," she said.

This was a simple way to reduce energy bills and help improve the neighbourhood

"It's much less expensive to heat a house [in winter] than to air condition in summer," Ms Jacobs said.

What to do when a heatwave hits

When the mercury rises, day or night, there are many things you can do to stay cool.

Mr Goldie said it was important to look out for people around us who were more vulnerable.

"People are very vulnerable when they're socially isolated," he said.

"We see a lot of older folks who would be much better off if they had people checking in on them.

"It's great to check in on your friends and family, see if someone needs a couch under an air conditioner to sleep on a hot day or hot night."

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